The present invention relates to an instrumentarium for implanting a tendon replacement, especially a crucial ligament replacement in a knee-joint, having a button that can be placed against an outer opening of a bone channel in which the tendon replacement is arranged. The button comprises openings through which fixation threads of the tendon replacement can be threaded, and comprises further a central projection that extends into the outer opening of the bone channel when the button is applied against the latter.
An instrumentarium of this kind, and a corresponding operation technique in which that instrumentarium is employed, is known from the compendium “Michael Strobel; Arthroscopic Surgery”, pp. 398 to 444 “Operation Technique”, Springer-Verlag Berlin Heidelberg 1998. Such an instrumentarium has also been described in Applicant's German Patent Application No. 198 51 152.3, filed on Nov. 6, 1998.
For implanting a crucial ligament replacement in a knee-joint one produces a drilled channel, at a flexion angle of the knee-joint of approximately 60 to 90°, that extends through the distal end of the femur and also through the proximal end of the tibia. One then inserts into that drilled channel the tendon replacement, which is a natural tendon of the respective patient, for example the semitendinosus tendon. Fixation threads sewn to the ends of the tendines project from both ends of the drilled channel and serve to fix the tendon in place. The threads, which project from the outside of the femur, are usually fixed by means of a plate that rests against the outer opening of the drilled channel. The fixation threads projecting from the opposite end of the drilled channel, i.e. on the outside of the tibia, are fixed by means of what is known as a tibial button. This device for retaining the sutures is what is meant throughout this specification by the term “button”.
The button has the general shape and size of a shirt button, which means that it comprises a circular main body having substantially the shape of a disk or the rim of a plate, with a central curved portion projecting on its one side and a corresponding depressed portion provided on its opposite side. The central portion is provided with openings through which the fixation threads can be threaded. A button of this kind is applied against the drilled channel so that its projection or curved portion comes to rest partially in the drilled channel. The fixation threads are threaded through the openings or holes, and are knotted in the manner illustrated by the respective sequence of operational steps shown in Strobel, loc. cit., p. 417. Regarded from the side, the contour of such a button is such that the projection rises, starting from its outer edge, along a smooth curvature to a rounded bulge from where it drops on the diametrically opposite side along a corresponding symmetric smooth S-shaped line.
It is a disadvantage of such a button that its central projection is supported in the opening of the drilled channel roughly along the latter's circumferential edge only so that it may get displaced, in particular get tilted, under load.
After the fixation threads threaded through the holes of the button have been knotted on the outside, the button so fixed can be turned a little in order to slightly increase the tension of the tendon. However, due to the fact that the button is supported in the outer opening of the drilled channel only along an outer circumferential line (see FIG. 14 of the present application), it is not guaranteed that the frictional engagement so produced will be sufficient to safely prevent the button from turning back and, thus, the tension of the tendon from being slackened.
EP-A-0 865 774 discloses an anchoring element intended for being connected to fixation threads of a tendon replacement, which is shaped as an oblong body that extends diametrically across the outer opening of the drilled channel and beyond both sides of the latter. The sections of the body that extend beyond the two sides of the outer opening are provided with nail-like elements that project toward the bone and that serve for being driven into the latter. The anchoring element is, therefore, nailed in place so that it extends transversely across the outer opening. In the area of the outer opening, the oblong body comprises a V-shaped recessed portion that projects into the drilled channel. The groove formed by the “V” receives the ends of the fixation threads which are knotted therein. It is a disadvantage of that arrangement that the anchoring element cannot be turned any more after the fixation threads have been knotted in the described element in order to tension the tendon, because the tendon is fixed against rotation by the nail-like pins that have been driven into the bone. In addition, the anchoring element is complex in shape and correspondingly expensive to produce.
Now, it is the object of the present invention to improve an instrumentarium for implantation of a tendon replacement so that the tendon replacement can be implanted easily, but yet correctly and safely seated.